setdisplay(320,200,32,1):paper(0xFFFFFF):ink(0x000000):pen(0x000000):cls
screenopen(1,104,128,  0,0,104,128,0):paper(0x77FFFF):ink(0x000000):pen(0x000000):cls
screenopen(2,104,128,104,0,104,128,0):paper(0xFF77FF):ink(0x000000):pen(0x000000):cls
screenopen(3,104,128,208,0,104,128,0):paper(0xFFFF77):ink(0x000000):pen(0x000000):cls
   paper(0xFFFFFF)
while key(27)=0
   b=int(rnd(4)):screen(b)
   screenviewport((b-1)*104,0,104,rnd(128),0)
   locate(1,1):prints(str$(screenviewporth)+"   ")
   waitvbl:wait(250)
 wend
